Robert Trivers laid the groundwork for much of sociobiology, evolutionary psychology and sociological game theoretical examinations of selection pressures way back in the early 70's.
One fascinating insight is that during the arms race between cheats and trusters in the cooperation game, it is likely that people will be selected for (as cheats) who actually deceive themselves about their own intentions to cheat, so that others, who have been selected to detect cheaters by their unconscious facial expressions, body language, and usage of verbalizations, would be hindered in their detection of such cheats.
Or as popular sayings go, "A good con artist believes his own con."
It's easy to believe this about the other side.
How many of us are deceiving ourselves?
Just askin'.